With the release of Windows 10 v1909, Microsoft released a set of generic keys to encouraging anyone who wants to dive in to try out. It’s perfect for use in a test environment using virtualization technology, i.e. Hyper-V.
Here is a set of keys for Windows 10 OEM images, the ones you can download using Windows 10 Media Creation Tool. Thanks to Winaero.
But for organizations that use volume licensed editions along with Key Management Service, these are the keys to go.
Additionally, if you also want to try out Windows Server 2016 or 2019, here are the ones to use.
Note that these keys are only good for testing purposes for a short period of time, usually up to 90. Once you are done and ready to activate, go to Settings > Update & Security > Activate > Change product key.